1. Field of the Invention
This invention relates in general to catheters for removing obstructions from vessels carrying body fluids and, more particularly, to a hydro-rotary vascular catheter for removing plaque from blood vessels.
2. Description of the Prior Art
The removal of harmful blockages from ducts and passages within the body is typically accomplished by one of two conventional techniques. The first technique, called balloon angioplasty, utilizes a treatment catheter equipped with two inflatable balloons which seal off a constricted area in a duct or passage such as a blood vessel. An inlet member is provided within the catheter for supplying a suitable solvent, such as a solution of digestive enzymes, to the area delimited by the two balloons, and an outlet member is provided for removing the dissolved material from the area. In addition, a second supply channel is provided for allowing the blood or other body fluid to bypass the delimited area, thus preventing a complete coronary obstruction. Representative examples of this type of catheter are found in U.S. Pat. No. 4,423,725 to Baran et al, U.S. Pat. No. 4,445,892 to Hussein et al, and U.S. Pat. Nos. 4,573,966 and 4,610,662 to Weikl et al.
A major problem with the above type of catheter is that the solvent used to remove the obstruction may attack the walls of the blood vessel itself as well as the harmful substances it is intended to dissolve. This can lead to perforation or rupturing of the blood vessel, which can endanger the life of the patient.
The problems associated with balloon angioplasty have led to the development of a second technique, known as laser angioplasty, which uses laser energy rather than a chemical solvent to vaporize the obstruction. A typical example of a laser angioplasty catheter is described in U.S. Pat. No. 4,685,458 to Leckrone. In Leckrone, the catheter, which is mounted for rotation and translation about a filament, has a pair of abutments disposed on its distal end. Also included on the distal end of the catheter is a bladder which, when inflated, causes the abutments to bear against the inner surface of the blood vessel so that the space between the abutments defines a working chamber for delimiting the area around an obstruction. A fiber optic connected to a source of laser energy extends through the catheter, with the distal end of the fiber optic being disposed in one of the abutments. In addition, a suction port is provided between the abutments for removing disintegrated material from the delimited area. Severing means such as a blade or heated element may also be included for severing and releasing material which is not vaporized by the laser.
Like balloon angioplasty, however, laser angioplasty can result in perforation or rupture of the blood vessel itself unless great care is taken to control the intensity and level of the laser energy as well as the direction in which the energy is emitted.
In response to the above problems, a third type of catheter has been introduced. This catheter, disclosed in U.S. Pat. No. 4,631,052 to Kensey, comprises a bladed cutting head which is rotated by turbine drive to cut away occlusions in a body vessel. However, this catheter poses a potential danger to the patient if the rotary head should happen to bounce off an especially hard portion of an occlusion and cut through a vessel wall.
Accordingly, there exists a need for a new and improved vascular catheter which overcomes the shortcomings of the prior art.